000
FXUS61 KBTV 172004
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
404 PM EDT Sat Mar 17 2018
.SYNOPSIS...
High pressure will deliver a fairly quiet, albeit cold, start
to the week. Still watching a coastal low that will develop
midweek, however current indications are that this low will
remain well to our south and be a non-factor for us in the North
Country. Temperatures will be around 10 to 20 degrees F below
normal, with the cold temperatures lasting through the week as
we remain under predominantly northwesterly flow.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 355 PM EDT Saturday...A look at regional observations this
afternoon paints the picture, showing a distinct cold front
working its way south over southern Vermont and the North
Country of New York. Along and behind the front, temperatures
have dropped or remained fairly steady through the morning and
gusty northwesterly winds peaked this afternoon. Once the sun
sets this evening, the deeply mixed boundary layer will
decouple, allowing a surface inversion to develop. This will
result in rapidly decreasing winds this evening along with
plummeting temperatures tonight. Persistent northwesterly flow
will continue to tap into a continental polar airmass over
Quebec, pulling unseasonably cold air southeastward into New
England. 925 mb temps overhead will fall to between -16 and -19
C. Surface winds will taper off as ridging builds, however the
center of the high pressure will remain well to our northwest
over Central Canada, so not expecting calm winds. Somewhere in
the 5-10 knots range would make sense, which would limit the
degree of radiational cooling that can be achieved overnight.
Also working against maximum radiational cooling will be some
lingering low level moisture that hiRes models are indicating
may remain trapped below the inversion overnight. All these
factors taken into account, it`s still going to be a cold night.
Have knocked down forecast temperatures to below guidance as
models rarely capture the degree of cooling in setups like this.
However, the forecast hinges on how much moisture remains
trapped in the surface layer; if we`re able to dry out
completely, forecast won`t be cold enough. Current thinking is
that we`ll see temperatures drop into the lower single digits
below zero in the northern Adirondacks and the Northeast
Kingdom, while the rest of Vermont and the Saint Lawrence Valley
will bottom out in the single digits above zero. Will be
monitoring cloud cover through the night and adjust forecast as
needed.
By Sunday morning, a weak surface low will enter the forecast
picture. This low and its associated clouds are currently
visible on satellite imagery over central Ontario. Overnight,
expect the weak system to continue on its southeastward track
and move into western New York by Sunday morning. The better
impacts of this low will remain to the southwest of our forecast
area, however we can expect some increasing clouds during the
day over northern New York and then into southern Vermont and
maybe an isolated snow shower or two as the system passes by to
our south and west. After this feature clears the forecast area,
we should be drier as ridging once again builds from central
Canada.
&&
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 335 PM EDT Saturday...This period will feature much below
temperatures and dry conditions as cold northwest flow prevails
with sfc high pres anchored just south of Hudson Bay. The
forecast challenge for Monday into Monday Night will be
temperatures as position of sfc high may keep atmosphere just
mixed enough to prevent temps from completely bottoming out.
Progged 850mb temps modify slightly by 18z Monday with values
btwn -13c and -16c, which with good mixing and sun should result
in high temps mid teens mountains to mid 20s valleys with a few
upper 20s possible. Still 10 to 15 degrees below normal for
mid/late March, normal high at BTV is near 40f by early next
week. Still some gradient with position of sfc high pres to our
northwest on Monday Night...but with clear skies thinking winds
will decouple in protected valleys with lows -5F NEK/SLK to
lower teens CPV/SLV and lower CT River Valley. However, would
not be surprised with a few readings between -10f and -15f by
early Tuesday Morning if high clouds can stay to our south.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 335 PM EDT Saturday...Long term will continue to support mean
mid/upper level trof across the eastern conus with undefined
split flow between northern and southern streams. Latest
guidance shows northern stream jet with northwest flow aloft
prevails across the northern Great Lakes into the NE CONUS with
no interaction with southern stream...which should keep the
storm track to our south this upcoming week. This pattern
supports much below normal temps and limited chances for
precip...and is very similar to our pattern in early January,
except now we are in mid/late March and temps will be warmer.
Interesting GFS bukfit for BTV shows only 0.01 qpf through 12z
Thursday...indicating how dry the northwest flow will be. Still
have to watch southern stream energy ejecting toward the mid
atlantic states and associated sfc low pres...but all guidance
shows this system staying to our south attm...with no real
northern stream interaction. The upper level pattern and
associated pieces of short wave energy becomes very complex and
messy toward mid week, which results in plenty of uncertainty.
The combination of departing low pres southeast of the BM and
high pres anchored over Hudson Bay will help to provide region
with a modifying arctic air thru late week. ECMWF and GEM are
much more aggressive with deepening trof and associated low
level caa for next weekend with another shot of reinforcing cold
air possible...which seems reasonable given upper level
pattern. Progged 850mb temps warm between -8c and -10c by
midweek supporting highs back into the mid 20s to mid/upper 30s.
Little change anticipated in 925mb to 850mb thermal profiles
through most of the week and into early next weekend. Temps will
slowly modify toward normal levels by Friday...before
additional cooling arrives next weekend or early the following
week.
&&
.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
Through 18Z Sunday...Primarily VFR conditions will persist
through the TAF period with the main aviation concern being
gusty northwesterly winds this afternoon. Expect winds to
decrease to the 10-20 knot range around 22Z, and then slacken to
under 10 knots overnight as high pressure builds in. A few
isolated snow showers are occurring amid the unstable
atmosphere this afternoon, but these will weaken by evening as
the atmosphere stabilizes. Any areas that do see a snow shower
could see conditions temporarily drop to MVFR/IFR, but the
deterioration of flight conditions would be short lived due to
the isolated nature of the showers. After 00Z, expect dry
weather and VFR conditions through the remainder of the TAF
period.
Outlook...
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: Mainly VFR, with areas MVFR possible. NO SIG WX.
Wednesday: Mainly MVFR, with local IFR possible. Slight chance
SHSN.
Wednesday Night: Mainly VFR, with local MVFR possible. Slight
chance SHSN.
Thursday: Mainly MVFR, with local IFR possible. Slight chance
SHSN.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...RSD
NEAR TERM...RSD
SHORT TERM...Taber
LONG TERM...Taber
AVIATION...RSD